The ornamental design for a watch, as shown and described.
FIG. 1 is a perspective view of the watch showing my design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The structural features depicted by broken lines have been shown for the purpose of illustrating portions of the watch that form no part of the claimed design.